Figure 1. Compression or tubular type weatherstripping and sweep weatherstripping on a window.
Weatherstripping is a very simple and relatively low-cost way to improve the energy efficiency of a home by reducing air leaks through doors and operable windows by sealing the movable connections when the door or window is closed, providing better protection against air drafts. Estimates show that air leaks due to improperly sealed and weatherized homes account for 30-40% of a home's overall heating and cooling loss. As well as letting warm or cool air travel from its desired location, air drafts and leaks damage the homes insulation since warm, moist air leaving the house can dampen the insulation. This in turn reduces its effectiveness.
Weatherstripping is simply a word applied to a series of different types of materials and seals that perform the same basic task. It comes in many forms, and can be made from a series of materials such as wood, rubber, vinyl, metal, and foam. Each type of material has its strength and weaknesses, and some are best used in certain situations. There are a few main designs of weatherstripping, which are:
- V-Strip: This type of weatherstripping is composed of a large strip of material folded back along itself and is made of metal or vinyl. This type is durable, long lasting, easy to install, and works better when retrofitting older homes. Many come with an adhesive back and is pressed along the frame without the use of tools. More expensive bronze versions are available and provide a better seal, however they must be nailed down into place.
- Adhesive-Backed Tape: This rubber or foam based weatherstripping is sold in several different widths and thicknesses, and is "stuck" onto the seal of a window or door through self-adhesive tape. This type of weatherstripping is among the easiest to install as it is cut to the designed length and attached to the door or window by its adhesive back. This type is best suited for irregular-sized openings, but wears out quickly.
- Felt: This felt-based weatherstripping can be plain or reinforced with a small metal strip and is sold in rolls that are cut and stapled into place. These must be installed so that the seal presses against it. These strips are relatively delicate, need replacing every 1-2 years, and cannot be used in places where it will be exposed to moisture or where there is excessive abrasion. This type of weatherstripping is very visible where applied.
- Interlocking Metal: This type of weatherstripping provides the best seal but is complex to install and more expensive than other options. For this model, two V-strip type pieces of weatherstripping are placed on the door and frame, and interlock to seal tightly when the door is closed. Installation of this type is typically done by professionals.
- Tubular Rubber and Vinyl: This type of weatherstripping can also be called compression weatherstripping, and is shown in Figure 1. Here, small tubes of rubber and vinyl are placed on the edges where a seal is needed and provide this tight seal when the door or window pushes against the tube. In general, these are moderately resilient and last around 5 years. This type of weatherstripping can be more difficult to install than adhesive-backed tape.
- Thresholds: The floor underneath an exterior door generally has a raised seal known as a threshold, and many of these have weatherstripping built in. Generally tubular rubber weatherstripping is used here.
- Door Sweep: This seal is composed of an aluminum or stainless steel base with a plastic, vinyl, sponge, or felt brush. The sweep is applied to the bottom side of a door to block out drafts from the bottom of the door. A door sweep is fairly easy to install and types can be purchased for an uneven door. However, the more advanced the sweep is the more costly it is, and they can also be fairly visible and drag on carpet.
Some new doors do come with factory-applied weatherstripping, although over time the effectiveness of this stripping may be reduced and air leaks may once again become an issue. However, many doors and windows have little to no weatherstripping or weatherstripping that no longer performs as well as it could.
Knowing how to tell if the seal on a door or window is important if drafts are to be detected. To check if a door or window may be leaking due to insufficient or improperly applied weatherstripping, close the door on a piece of paper. If you need to put some effort to pull the paper out, the weatherstripping is likely providing a good seal. If you can pull the paper out very easily, the weatherstripping is likely not tight enough or in good shape. As well, check to see if the weatherstripping is soft and pliable to mould to the shape of the door or window and provide a good seal. Finally, if you cannot see any daylight or feel any drafts coming through the window or door, the seal provided by the weatherstripping is likely good.
Before new weatherstripping is added, it is important to remove the old, ineffective weatherstripping.
Locations of Other Leaks
Although it may be obvious to check the seals of windows and doors for leaks, air leakage can occur in some obscure places. Electrical outlets actually allow cold air into the house and leak cold air out during the summer. Caulking or pre-cut tubular rubber or foam seals can be applied behind the switch or plug plate to reduce leaks. As well, seals should be checked around window air conditioners, chimneys, openings where electrical and telephone wires enter the building, and where the walls meet the foundation.
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